• Seeds changed the course of plant evolution
  • Gymnosperms evolve ~360 mya
  • climate became drier = selection pressures
  • Elkensia first fossil seed plant

• Seeds consists of embryo & nutrients
  • surrounded by protective coat
  • seeds can be dispersed long distances
  • less dependence on water

• 2 living seed lineages
  • gymnosperms (naked seed)
  • angiosperms (covered seed = fruits)

• Reduction of gametophyte
  • mosses → ferns → seed plants
  • gametophyte become microscopic

• Heterosporous life cycle
  • 2 kinds of spores
  • form male/female gametopytes

• Ovules
  • megasporangium kept inside sporophyte
  • ovule contains megaspore

• Pollen
  • microspore develops into pollen grain

• Cycads: 300 living species
  • earliest evidence of insect pollination
  • Cycads and dinosaurs lived together

• Gnteophytes: small and super weird group
  • some flowering traits

• Ginkos: Ginkgo biloba is only species left!
  • landscapers only plant males because…

• Conifers: ~600 species (cones)
  • evergreen and deciduous
  • leaves are needles or scales

• Male and female cones on same plant
  • sporophyll → sporangia → spores
  • scales → modified leaves → sporophyll
  • pollen (male) and ovulate (female) cones

• Male cones house microsporangium
  • microsporangium produces microspores
  • microspores develop into pollen grains
  • male gametophyte inside pollen grain
  • pollen dispersed by wind

• Female cones have 2 ovules per scale
  • each ovule has megasproangium
  • megasporangium produce 4 megaspores
  • 1 megaspore survives

• Pollen grain reaches ovule and germinates
  • pollen tube grows toward megaspore
  • megaspore develops gametophyte with egg
  • sperm → pollen tube → egg
  • seed forms, dispersed by wind

• Most diverse living group of plants
  • 14,000 genera, 350,000 species
  • 94% of plant diversity

• 2 classes: Moncots and Dicots
  • monocots = one seed leaf in embryo
  • dicots = two seed leaf in embryo

• Flower is a modified stem for reproduction
  • with 4 types of modified leaves

• Sepals: leaves at base which enclose flower
  • usually green

• Petals: colored leaves to attract pollinators
  • less colored if wind pollinated

• Two types of fertile organs to make spores
  • sporophylls (male and female)

• Stamens: microsporophylls
  • produce microspores that develop into pollen

• Anther: where microsporangia develop
  • microspores produced
  • microspores → pollen
  • pollen → male gametophyte

• Filament: stalk that holds the anther

• Carpel: megasporophyll

• Stigma: receives pollen
  • sticky

• Style: leads from stigma to ovary
  • where pollen tube forms

• Ovary: contains ovules
  • megasporangium inside ovule produce 4 megaspores
  • 1 megaspore survives to make female gametophyte